1. Field of the Invention
The present invention relates to a one-to-multitude communication method by mobile phones and other communication terminals, a communication system of the same, and a communication terminal for performing one-to-multitude communications.
2. Description of the Related Art
In recent years, the modes of communication by phones have become greatly diversified. Phones able to perform packet communications utilizing the IP (Internet Protocol) network are being widely utilized in addition to conventional speech by circuit switched connection. For example, Japanese Patent Publication (A) No. 2003-174520 discloses “Chat Mail” for conversation between mobile phones by exchanging text in real time. Chat Mail is one of the modes of communication called “group communication” were pre-registered members form a group and transferring text and other data in real time in the group.
In this group communications, attempts have been made for speech by utilizing VoIP (Voice Over Internet Protocol). One of these is called the PoC (Push to Talk Over Cellular). In the PoC, an SIP (Session initiation Protocol) server manages each group and each member in the group and control voice calls in a packet format.
When performing one-to-multitude communications in such group communications, usually only one communication terminal permitted by a server system can transmit data (for example audio data) to the other communication terminals. When a plurality of communication terminals simultaneously try to transmit data, in general the server system selects one communication terminal for transmission permission according to a certain rule. For example, it considers for example the number of times transmission was desired in the past and rejected and sets a priority order of permission of transmission for terminals so as to enable as fair transmission by the terminals as possible.
Even when the server system sets such a fair priority order, on the communication terminal side, requests for transmission permission continue to be unilaterally rejected by the server system as usual, therefore a user of a communication terminal cannot estimate when transmission will permitted and sometimes feel dissatisfied.
Further, each time a request for transmission permission is rejected by the server system, the communication terminal must issue another request to the server system, therefore the operation is troublesome.